let canvas = document.getElementById('canvas'),
    ctx = canvas.getContext('2d');
cw = window.innerWidth,
    ch = window.innerHeight,
    fireworks = [],
    particles = [],
    hue = 120,
    limiterNow = 0,
    limiterTotal = 30;

canvas.width = cw;
canvas.height = ch;


function random(min, max) {
    return Math.random() * (max - min) + min;
}

function calculataDistance(p1x, p1y, p2x, p2y) {
    var xDistance = p1x - p2x,
        yDistance = p1y - p2y;
    return Math.sqrt(Math.pow(xDistance, 2) + Math.pow(yDistance, 2));
}

function Firework(sx, sy, tx, ty) {
    this.x = sx;
    this.y = sy;
    this.sx = sx;
    this.sy = sy;
    this.tx = tx;
    this.ty = ty;
    this.distanceToTarget = calculataDistance(sx, sy, tx, ty);
    this.distanceTraveled = 0;
    this.angle = Math.atan2(ty - sy, tx - sx);
    this.speed = 2;
    this.acceleration = 1.05;
    this.brightness = random(50, 70);
    this.targetRadius = 1;
    this.coordinateCount = 3;
    this.coordinates = [];

    while (this.coordinateCount--) {
        this.coordinates.push([this.x, this.y]);
    }
}

Firework.prototype.draw = function () {
    ctx.beginPath();
    ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length - 1][1]);
    ctx.lineTo(this.x, this.y)
    ctx.strokeStyle = 'hsl(' + hue + ',100%,' + this.brightness + '%)';
    ctx.stroke();

    ctx.beginPath();
    ctx.arc(this.tx, this.ty, this.targetRadius, 0, Math.PI * 2);
    ctx.stroke();

}

Firework.prototype.update = function (index) {
    this.coordinates.pop()
    this.coordinates.unshift([this.x, this.y])

    if (this.targetRadius < 8) {
        this.targetRadius += 0.3
    } else {
        this.targetRadius = 1
    }
    this.speed *= this.acceleration;

    let vx = Math.cos(this.angle) * this.speed,
        vy = Math.sin(this.angle) * this.speed;

    this.distanceTraveled = calculataDistance(this.sx, this.sy, this.x + vx, this.y + vy);

    if (this.distanceTraveled >= this.distanceToTarget) {
        fireworks.splice(index, 1)
        createParticle(this.tx, this.ty)
    } else {
        this.x += vx;
        this.y += vy;
    }

}


function particle(x, y) {
    this.x = x;
    this.y = y;
    this.angle = random(0, Math.PI * 2);
    this.speed = random(1, 10)
    this.friction = 0.95;
    this.gravity = 1;
    this.hue = random(hue - 20, hue + 20)
    this.brightness = random(50, 80)
    this.alpha = 1;
    this.decay = random(0.015, 0.03);
    this.coordinates = [];
    this.coordinateCount = 5;
    while (this.coordinateCount--) {
        this.coordinates.push([this.x, this.y])
    }

}
particle.prototype.draw = function () {
    ctx.beginPath();
    ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length - 1][1]);
    ctx.lineTo(this.x, this.y)
    ctx.strokeStyle = 'hsla(' + hue + ',100%,' + this.brightness + '%,' + this.alpha + ')';
    ctx.stroke();
}
particle.prototype.update = function (index) {
    this.coordinates.pop()
    this.coordinates.unshift([this.x, this.y]);
    this.speed *= this.friction;
    this.x += Math.cos(this.angle) * this.speed;
    this.y += Math.sin(this.angle) * this.speed + this.gravity;

    this.alpha -= this.decay;
    if (this.alpha <= this.decay) {
        particles.splice(index, 1)
    }
}

function createParticle(x, y) {
    let partcicleCount = 100;
    while (partcicleCount--) {
        particles.push(new particle(x, y))
    }
}





function run() {
    hue++;
    ctx.fillStyle = 'rgba(0 ,0 ,0 ,0.5)';
    ctx.fillRect(0, 0, cw, ch);
    var i = fireworks.length;
    while (i--) {
        fireworks[i].draw();
        fireworks[i].update(i)
    }

    var k = particles.length;
    while (k--) {
        particles[k].draw();
        particles[k].update(k)
    }

    if (limiterNow >= limiterTotal) {
        fireworks.push(new Firework(cw / 2, ch, random(0, cw), random(0, ch / 2)));
        limiterNow = 0;
    } else {
        limiterNow++;
    }
}



canvas.addEventListener('mousedown', function (e) {
    var mx = e.pageX - canvas.offsetLeft;
    var mt = e.pageY - canvas.offsetTop;
    fireworks.push(new Firework(cw / 2, ch, mx, mt));
})

canvas.addEventListener('touchstart', function (e) {
    var mx = e.pageX - canvas.offsetLeft;
    var mt = e.pageY - canvas.offsetTop;
    fireworks.push(new Firework(cw / 2, ch, mx, mt));
})


setInterval(run, 33)
